1. Field of the Invention
The present invention relates to a workpiece clamping jig and a workpiece machining method using the workpiece clamping jig.
2. Description of the Related Art
Conventionally, jigs configured to hold workpieces by suction and attachment jigs for clamping workpieces are used as workpiece clamping jigs, besides mechanical clamping jigs, such as a stock vice. Since these attachment devices are susceptible to the problem of deflection or deformation of workpieces caused by mechanical clamping, they are often used to clamp thin-walled workpieces. Conventional attachment methods are based on vacuum suction or magnetic attraction (for magnetic workpieces). In vacuum suction jigs, vacuum suction is performed by applying negative pressure to a workpiece by means of a suction device such as a vacuum pump and suction through-holes in a workpiece mounting surface of the jig. One example of such a vacuum suction jig is disclosed in Japanese Patent Application Laid-Open No. 2000-126960.
The vacuum suction jig of Japanese Patent Application Laid-Open No. 2000-126960 described above is designed so that the suction through-holes in the workpiece mounting surface need not be separately closed even though the suction holes are located outside the attachment surface of the workpiece. In this jig, a slidable presser plate laterally holds and fixes the workpiece.
The performance of the vacuum suction jig disclosed in Japanese Patent Application Laid-Open No. 2000-126960 is based on a combination of mechanical clamping of side surface portions of the workpiece and vacuum holding of a bottom surface portion of the workpiece. Since the surface roughness and flatness of an attachment surface and abutting surfaces of the jig and the perpendicularity between the surfaces are not ensured, however, the bottom surface of the workpiece may possibly be lifted by mechanical clamping. The vacuum suction jig for use as a cutting jig is intended to bring the workpiece into close contact with the workpiece mounting surface, thereby preventing the bottom surface portion of the workpiece from being plastically deformed or caused to vibrate by machining load. Therefore, it is important to ensure close contact between the bottom surface of the workpiece and the workpiece mounting surface of the jig.